I am quite aware and do you know what happens when you see an entire river of particle effects in your FOV? Your system will lag horribly and most likely crash on anything less than the best of computers. Sure, my computer could run it without lagging but Johnny Knocker down the street with a good computer but not a high end gaming computer watches as his computer catches fire. From what people have said, they want the entire water as spray particles. If people don't see the particle effects in the water, watch the video again. You can see as it moves, which the water looks great as what it is supposed to be, white water, and it has spray particle effect where it collides with rocks and what not. They did great with the white water rapids but some people don't have an eye for detail.
It's not like that water is their moving water, their moving water you can see in other scenes like the cave where he is launching a light spell from the staff or the waterfall in the cave where he makes a massive fiery explosion with a spell. Their moving water looks great, but that "waterfall" wasn't their moving water, it was white water rapids, which if you know what it's supposed to be it looks great.
I'm afraid I'm going to have to disagree. I don't think even top computers would be able to handle a fully realized water particle system, even if it was just in FOV. The time and power to render an animation sequence of water particles is sufficient to make me think that a real time water particle system in a game environment is still years away.
In a scene like that river, even using large particles that would result in a rather globular effect, we'd be talking tens of thousands, if not hundreds of thousands of particles interacting with each other and the environment. Just calculating the interaction of the particles would take a lot of power. Add onto that the lighting and rendering effects that would be applied to each one, it would be way too much to do in real time.